Bustamite

Kanoiri Mine

Kusagyu, Kanuma city, Tochigi pref., Japan

Field of view: 40 mm. Massive aggregate of bustamite. The specimen is composed of columnar groups of bustamite fibers. Bustamite at the top of the specimen turns darker by weathering. Bustamite is more easily weathered than similar appearance minerals such as rhodonite.

Recovered from a chert-hosted bedded Mn deposit subjected to Pyroxene facies contact metamorphism by S-type (Ilmenite-series) granodiorite. Formed in the Late Cretaceous (83 Ma).

Bustamite from this location was described in 1962.

Other localities

List of Japanese bustamite localities

Chichibu Mine (Hydrothermal Skarn, Fibrous)
Kusama Mine (Bedded Mn, Massive)
Kanoiri Mine (Mn Skarn, Fibrous)
Shirane Mine (Mn Skarn, Fibrous)